The Oklahoma senator and obstetrician known as “Dr. No” has taken on the most unlikely of roles: getting Republicans to say “yes” to tax hikes.

Tom Coburn, who has blocked dozens of bills, infuriated Democratic leaders and been on the lopsided end of some 96-3 votes, has been encouraging fellow Republicans both publicly and behind the scenes to break with the anti-tax orthodoxy that has come to define — some say hamstring — the modern GOP.

Coburn, 64, isn’t new to this call — he voted two years ago for the Simpson-Bowles plan that would have allowed tax rates to rise on top earners. Yet with a possible tax-hike vote in sight, Coburn has emerged as a Sherpa of sorts for reluctant conservatives to discuss a deal that includes higher tax rates on upper-income Americans in exchange for significant spending cuts and sweeping entitlement reforms.

In an interview, Coburn said the GOP should swallow hard and accept a smaller tax hike that would have the least effect on the economy. Without a deal, he warned, it’s “inevitable” all Americans will face an increase to their income tax rates when the 2001 and 2003 George W. Bush tax cuts expire Dec. 31.

And polls show Republicans would shoulder most of the blame if the two sides fail to strike a deal.

“I’m for raising revenue because we have to — it’s not because we should but because we have to,” Coburn told POLITICO. Republicans can say they refuse to support any tax hikes, “but it’s still going to happen. That’s what the law is.”

Last week, Coburn acknowledged on MSNBC’s “Morning Joe” that Republicans “have to raise revenue” and that he preferred that rates go up for families making more than $250,000 rather than capping deductions. On Sunday, he told ABC’s “This Week” that he was willing to accept a tax increase as part of a deal to solve the nation’s debt crisis.

Lawmakers know they’re largely observers to the ongoing negotiations between Obama and House Speaker John Boehner. But Coburn’s public push for revenues — anathema to anti-tax purist Grover Norquist and the GOP’s conservative base — has given other leading conservatives cover to speak in support of the tax-hike issue.

In an interview with Bloomberg Television that aired over the weekend, Sen. Mike Johanns (R-Neb.) signaled he’s open to raising rates on the top 2 percent of income earners — something Obama has demanded be part of any fiscal cliff deal. And Sen. Bob Corker (R-Tenn.), speaking on “Fox News Sunday,” said giving the president his tax hike on the wealthy, then tackling entitlement reform, appears to be “the best route for us to take” in fiscal cliff negotiations.